Arterial oxygen saturation in chronic congestive heart failure

Abstract

Continuous, 24-hour, ambulatory pulse oximetry was used in 10 subjects with New York Heart Association functional class II to III heart failure and in 5 age-matched controls to test the prevailing view that arterial oxygen saturation is preserved during wakefulness in chronic mild to moderate heart failure. Subjects with heart failure were stabilized on digitalis and diuretics at the time of the study. All subjects maintained time-activity logs, with an emphasis on self-reported sleep and wakefulness. A desaturation event was defined as a decrease in arterial oxygen saturation ≥4% from baseline lasting >5 seconds. Variables assessed included total desaturation events, decrease in arterial oxygen saturation duration/event, nadir of arterial oxygen saturation/event, and desaturation index ([cumulative desaturation time/total monitoring time] × 100). The ratio of self-reported wakefulness: sleep desaturation time was 47:53% for subjects with heart failure versus 64:36% for controls (p = NS). Mean (±SEM) time of arterial oxygen saturation <90% was 123 ± 67 minutes for subjects with heart failure versus 22 ± 25 minutes for controls (p < 0.01). Total desaturations were 220 ± 63 and 76 ± 35 (p = NS) for the heart failure and control groups, respectively. The heart failure group had a statistically, significantly greater decrease in arterial oxygen saturation, and a longer duration and deeper nadir of the desaturation event than did the age-matched control group. The desaturation index was 21 ± 3% and 4 ± 1% for the heart failure and control groups, respectively (p < 0.01). Both the heart failure and control groups showed a circadian pattern in arterial oxygen saturation profiles. It is concluded that arterial oxygen saturation is not preserved during self-reported wakefulness in chronic mild to moderate heart failure, showing significant desaturation events as compared with control subjects.